Hierarchical tunnels, e.g., label switched paths (LSPs), have been used to improve the scalability of tunneling networks, for example Multi-Protocol Label Switching (MPLS) Traffic Engineering (TE) networks. For instance, as the number of nodes and tunnels increases within a network, signaling burdens (tunnel set up/reroute/tear down/resize), resource consumption (e.g., memory), and state maintenance (e.g., refresh, etc.) become increasingly complex and taxing, particularly within network cores. The use of hierarchical tunnels, however, allows a plurality of tunnels (child tunnels, or “cLSPs”) that traverse a shared path segment (e.g., and have the same or compatible attributes/affinities) to be further encapsulated onto a single hierarchical tunnel (parent tunnel or “hLSP”), which may be less complex and less burdensome to maintain than the plurality of child tunnels.
While hierarchical tunnels offer various benefits that will be understood by those skilled in the art, various technical challenges are also presented with their use. For instance, protecting one or more child tunnels against failure of a head-end node of an associated hierarchical tunnel, e.g., such as for “Fast Reroute” (FRR), is currently inefficient and cumbersome. That is, a backup tunnel originating from a child tunnel would generally enter a hierarchical tunnel at “mid-tunnel” with an improper tunnel header (e.g., a label and/or label stack) primarily because the point of local repair (PLR) upstream of the hierarchical tunnel head-end node is on the child tunnel, while the merge point downstream of the hierarchical tunnel head-end node is on the hierarchical tunnel, as will be understood by those skilled in the art. One solution consists of setting up backup tunnels from each upstream node of the hierarchical tunnel head-end node to the tail-end node of the hierarchical tunnel, thus bypassing the hierarchical tunnel (e.g., due to required path diversity from the hierarchical tunnel). As a result, the general length of backup tunnels through the network is increased, and more of the network is traversed by tunnels thus increasing the number of tunnels per-node in the network. This may be considered a substantial waste of resources, and thus, the motivation for hierarchical tunnels is greatly reduced.